This disclosure relates generally to well servicing and completion systems for the production of hydrocarbons. More particularly, the disclosure relates to actuatable downhole tools including slideable sleeves for providing selectable access to open (uncased) and cased wellbores during completion, wellbore servicing, and production operations, such as hydraulically fracturing open and cased wellbores and perforating cased wellbores. The disclosure also relates to tools for selectively actuating slideable sleeves of downhole tools for providing selectable access to open and cased wellbores in wellbore servicing and production operations. Further, the disclosure regards tools for hydraulically fracturing a subterranean formation from multiple zones of a wellbore extending through the formation. The disclosure also relates to tools for selectably perforating components of a well string in preparation for hydraulically fracturing a subterranean formation.
Hydraulic fracturing and stimulation may improve the flow of hydrocarbons from one or more production zones of a wellbore extending into a subterranean formation. Particularly, formation stimulation techniques such as hydraulic fracturing may be used with deviated or horizontal wellbores that provide additional exposure to hydrocarbon bearing formations, such as shale formations. The horizontal wellbore includes a vertical section extending from the surface to a “heel” where the wellbore transitions to a horizontal or deviated section that extends horizontally through a hydrocarbon bearing formation, terminating at a “toe” of the horizontal section of the wellbore.
An array of completion strategies and systems that incorporate hydraulic fracturing operations have been developed to economically enhance production from subterranean formations. In particular, a “plug and perf” completion strategy has been developed that includes pumping a bridge plug tethered through a wellbore (typically having a cemented liner) along with one or more perforating tools to a desired zone near the toe of the wellbore. The plug is set and the zone is perforated using the perforating tools. Subsequently, the tools are removed and high pressure fracturing fluids are pumped into the wellbore and directed against the formation by the set plug to hydraulically fracture the formation at the selected zone through the completed perforations. The process may then be repeated moving in the direction of the heel of the horizontal section of the wellbore (i.e., moving “bottom-up”). Thus, although plug and perf operations provide for enhanced flow control into the wellbore and the creation of a large number of discrete production zones, extensive time and a high volume of fluid is required to pump down and retrieve the various tools required to perform the operation.
Another completion strategy incorporating hydraulic fracturing includes ball-actuated sliding sleeves (also known as “frac sleeves”) and isolation packers run inside of a liner or in an open hole wellbore. Particularly, this system includes ported sliding sleeves installed in the wellbore between isolation packers on a single well string. The isolation packers seal against the inner surface of the wellbore to segregate the horizontal section of the wellbore into a plurality of discrete production zones, with one or more sliding sleeves disposed in each production zone. A ball is pumped into the well string from the surface until it seats within the sliding sleeve nearest the toe of the horizontal section of the wellbore. Hydraulic pressure acting against the ball causes hydraulic pressure to build behind the seated ball, causing the sliding sleeve to shift into an open position to hydraulically fracture the formation at the production zone of the actuated sliding sleeve via the high pressure fluid pumped into the well string.
The process may be subsequently repeated moving towards the heel of the horizontal section of the wellbore (i.e., moving “bottom-up”) using progressively larger-sized balls to actuate the remaining sliding sleeves nearer the heel of the horizontal section of the wellbore. The balls and ball seats of the sliding sleeves may be drilled out using coiled tubing. The use of sliding sleeves and isolation packers disposed along a well string may streamline the hydraulic fracturing operation compared with the plug-and-perf system, but the use of varying size balls and ball seats to actuate the plurality of sliding sleeves may limit the total number of production zones while restricting the flow of fluid to the formation during fracturing, necessitating the use of high pressure and low viscosity fluids to provide adequate flow rates to the formation. Moreover, the use of multiple balls of varying sizes may also complicate the fracturing operation and increase the possibility of issues in performing the operation, such as balls getting stuck during pumping and failing to successfully actuate their intended sliding sleeve.